constancy vs constant

constancy and constant both are nouns.

Word	Noun	Adjective	Verb	Adverb
constancy	Yes	No	No	No
constant	Yes	Yes	No	No

constancy (noun)	constant (noun)
the quality of being enduring and free from change or variation	a quantity that does not vary
faithfulness and dependability in personal attachments (especially sexual fidelity)	a number representing a quantity assumed to have a fixed value in a specified mathematical context
(psychology) the tendency for perceived objects to give rise to very similar perceptual experiences in spite of wide variations in the conditions of observation

constancy (adjective)	constant (adjective)
	steadfast in purpose or devotion or affection
	uninterrupted in time and indefinitely long continuing
	unvarying in nature